mysql> create table test( sn int,
-> `createdTime` datetime NOT NULL COMMENT '创建时间',
-> `updatedTime` datetime DEFAULT NULL);
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 1199508
Current database: devops
Query OK, 0 rows affected (0.04 sec)
mysql> desc test;
+-------------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+----------+------+-----+---------+-------+
| sn | int(11) | YES | | NULL | |
| createdTime | datetime | NO | | NULL | |
| updatedTime | datetime | YES | | NULL | |
+-------------+----------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> insert into test values('1',null,null);
ERROR 1048 (23000): Column 'createdTime' cannot be null
mysql> insert into test values('1','2015-01-01 00:00:00',null);
Query OK, 1 row affected (0.00 sec)
mysql> select * from test;
+------+---------------------+-------------+
| sn | createdTime | updatedTime |
+------+---------------------+-------------+
| 1 | 2015-01-01 00:00:00 | NULL |
+------+---------------------+-------------+
1 row in set (0.00 sec)
mysql> alter table `test` modify column `updatedTime` datetime NOT NULL COMMENT '更新时间';
ERROR 1138 (22004): Invalid use of NULL value
